This invention relates to microprocessors in a control complex of the type which finds application in controlling the operation of a telecommunications switching system, and more particularly to the implementation of such a control complex so that a dialed number from a station served by the system results in the performance by the control complex of a designated system function.
Telephone switching systems have evolved to include various forms of computerized common controls of the programmable or stored program variety. Conventionally the computerized controls have been configured as multi-task monoprocessors with the result being the need to implement relatively complex control tasks and memory configurations. One of the characteristics of the monoprocessor approach is the need for an executive program or an executive processor for controlling system operations. Typically this results in a program which is interrupt driven thereby requiring a potentially complex hierarchy for the various interrupts. Moreover it is generally necessary to queue work for the purpose of distributing the real time work load of the processor. The resultant complexity of the programming task will be apparent from the foregoing, not only as it applies to initially generating and debugging the programs, but also in maintaining the system should a fault develop.
The present invention is related to and has particular utility when used in telecommunication switching system as described in the co-pending application Ser. No. 842,091 entitled Microprocessor Control Complex which has a multiprocessor control complex to provide distributed call processing. With such a control complex, the call processing functions are distributed among the processors in the complex in such a way as to modularize the control functions and simplify the programming.
While said co-pending applications are addressed to the overall configuration and hardware implementation of the control complex, and particularly the construction and operation under program control of the distributed processors which execute the operational functions of the system, as well as the interrelationship between the control complex and other portions of the switching system such as the digital switching network, the invention disclosed in the present patent application is primarily concerned with the provision in such a control complex of memory stores for the data base utilized by the processors in carrying out distinct, separate and widely varied operational functions under the direction of distinct and separate programs.
It is a fundamental characteristic of the telecommunication switching systems in which this invention is incorporated, that a directory number dialed at an originating station served by the system results in a certain pre-assigned function being performed by the system.
The primary object of the present invention is to provide memory structure and data organization for data utilized both in the invoking of programs for and carrying out of such programs by the processors of the control complex to execute designated operational functions in response to dialed directly numbers.
Another object is to provide a telecommunications switching system which requires no fixed numbering plan, but rather, permits a free and unconstrained numbering plan to be used, allowing, in essence, any one or more numbers in the numbering plan to call for the performance of a designated system function.
According to a further aspect of the invention, it is an object to economically implement telecommunications switching systems by configuring the control complex wherein the processors are commercially available microprocessor circuits and the data memory is provided by commercially available RAM circuits. Furthermore, an object is to simplify the structure of such a control complex by providing one of the microprocessors with its own program memory and also with the data base memory stores for the entire system.
While not limited to a telecommunication switching system having a multiprocessor implemented control complex, the present invention has particular utility in such a control complex, where a plurality of microprocessor control units are provided, each having a microprocessor and associated memory means. The various microprocessors are programmed to perform a portion of the total function of the switching system, so that the total function is distributed among the microprocessors. With this arrangement each microprocessor control unit may continue to perform the functions assigned to it independently and asynchronously of the other control units. Of course, it is necessary to transfer data between the control units for performance of the total switching function. To minimize the amount of time spent in interprocessor communication, and to decrease system complexity due to such communication, each microprocessor control unit is provided with an interprocessor buffer for receiving data from the associated microprocessor and for communicating data to the associated microprocessor. Means are provided for exchanging data between selected ones of the interprocessor buffers asynchronously of at least one of the associated microprocessors so that the microprocessors may continue to operate under program control while the buffers exchange data relatively independently thereof.
Another important object of the invention is to provide a system which simultaneously serves multiple "customer groups" with the same system hardware. By "customer groups" is meant separate groups of stations, typically on discrete sets of lines, served by the system. From all appearances to the user of the system, he has his own private system, even though a number of other "customer groups" or users are also sharing the same hardware. Thus, the use of the system including use of trunks, use of all features, and all recording and accounting of use is separately handled for each customer group.
A further object is to provide simultaneous service to more than one customer group, each with an independent directory number plan where the numbers used to designate functions in each customer group do not conflict with identical numbers used in another customer group to designate other system functions, yet allow cross-over between customer groups when desired.
While the invention will be described in connection with certain embodiments presently considered to be preferred, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents included within the spirit and scope of the invention as defined by the appended claims.